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Two consecutive experiments were conducted to test a hypothesis that mixed grazing outcome is influenced by the type of stocking system applied. The objective of both experiments was to investigate the influence of co-grazing with sheep on cattle liveweight gain (LWG) under continuous (C) and rotational (R) stocking, where sheep weekly liveweight change under the two stocking systems was kept similar. In experiment I nine yearling heifers (266 ± 4.5 kg liveweight) and 27 ewe hoggets (54±0.9 kg liveweight) were continuously stocked for 19 weeks on an irrigated perennial ryegrass-white clover pasture (2.95 ha) maintained at a sward surface height (SSH) of 5cm by adding or removing additional animals in a fixed ratio (1: 1 W⁰.⁷⁵ cattle:sheep). An equal area of pasture was rotationally stocked by a similar group of animals where they received a new area of pasture daily and also had access to the grazed area over the previous 2 days. The size of the new area provided daily was such that the weekly liveweight change of rotationally co-grazed sheep was equal to that of those continuously co-grazed with cattle. Similar groups of animals were used in the second experiment with additional group of 9 heifers grazed alone on C and R pastures. Liveweight of animals was recorded weekly and final fasted weight was determined after 24-hour total feed restriction. SSH on both treatment swards was recorded daily. There were three intake measurement periods spread over the trial period. Organic matter intake (OMI) was predicted from the ratio of N-alkanes in faeces and herbage. Diet composition was determined by dissecting oesophageal extrusa samples. Grazing behaviour (bite rates and grazing time) were also recorded. The mean SSH for C pasture was 5.1±0.09 cm. Overall pre- and post-grazing SSH for R pasture was 15.9 ±0.12 and 5.6 ±0.07 cm, respectively. As determined by the protocol average daily LWG of sheep was similar between C and R (147 (±5.8) vs 138 (±6.7) g day⁻¹; (P>0.05). In contrast, cattle continuously stocked with sheep grew 200 g day⁻¹ slower than those rotationally stocked with sheep (800 (±41.6) vs 1040 (±47.7) g day⁻¹, P<0.0l). R heifers achieved 30 kg higher final fasted liveweight than C heifers (350 vs 381 kg; P<0.01). Overall LWG per ha was also 6 % higher under R than C stocking (674 vs 634 kg ha⁻¹). The OMD of both sheep (73.5 vs 75.8 %) and cattle (75.8 vs 78.0 %) diets was similar under continuous and rotational stocking. There was no significant difference OMI data also concurred with the L WG data (Cattle: 7.94 vs 6.31 (±0.32) kg day⁻¹ (P<0.05); sheep: 1.40 vs 1.44 (±0.04) kg day⁻¹ for Rand C treatments, respectively). There was no difference in clover content of cattle diet under C and R treatments. C heifers had higher number of bites per minute than R heifers (62 vs 56; P<0.05). Proportion of heifers seen grazing (every 15-minute) during four 24-hour observations was greater on C than R pasture (0.44 vs 0.31 (±0.03); P<0.05). The similarity coefficient between sheep and cattle diet was 0.61 and 0.76 under C and R stocking, respectively. The lower daily LWG of C heifers was attributed to (a) the lower SSH under C than R stocking and/or (b) the inability of cattle to compete well with sheep where there is small, continual renewal of resources (C) in contrast to a large periodic renewal under R stocking. This experiment showed that the outcome of mixed gruing can be influenced by the stocking system chosen. But it was not possible to apportion the difference in LWG of cattle between mixed grazing per se and the difference in mean grazed sward height (5.1 for C vs 10.8 cm for R). A second experiment was conducted to determine the relative performance of cattle co-grazed with sheep (CS) and grazed alone (CA) under each stocking system. Hence, there were four treatments. CA- continuous stocking (CA-C), CS- continuous stocking (CS-C), CA- rotational stocking (CAR) and CS- rotational stocking (CS-R). A total area of 4.42 ha was allocated to each stocking system. Under C stocking, 2.95 ha (2/3) was assigned to CS-C and 1.47 ha (1/3) to CA-C, and SSH on both treatments was kept at 4 cm by adding or removing extra animals. Under R stocking, CA-R and CS-R grazed side by side separated by an electric fence. They were given a fresh area daily, the size of which was varied such that the weekly LW change of R sheep was equal to that of the C sheep. CA-R received one-third of the new area though the size was adjusted regularly to achieve the same post-grazing SSH with CS-R. Measurements included: weekly liveweight change, OMI (two periods) and diet composition (using N-alkanes). The mean SSH of CA-C and CS-C swards was 4.27 and 4.26 (±0.02) cm, respectively. CA-R and CS-R swards had mean pre-grazing SSH of 14.9 and 15.2 (±0.08) cm and post-grazing heights of 4.87 and 4.82 cm (±0.03), respectively. The proportion of areas infrequently grazed was higher for CA-C than CS-C swards (0.22 vs 0.17, respectively). C and R sheep daily LWG: 155 (±0.6) and 147 (±0.7) g, and OMI: 1.96 and 2.04 (±0.ll) kg, respectively, were not significantly different. They also had similar diet composition. In comparison, CS-C heifers grew only at 69 % of the daily LWG achieved by CS-R heifers (706 vs 1028 (±72) g; P<0.05). LWG of CA-C and CA-R was 916 and 1022 (±72) g day⁻¹, respectively. The difference in LWG between CS-R and CS-C (D₁) heifers was due to difference in mean sward height, stocking system and mixed grazing, while D₂ (difference in LWG between CA-R and CAC) was due to difference in mean sward height and stocking system. D₁-D₂ (the effect of stocking system on mixed grazing) was 216 g and made up 67 % of the total difference between CS-R and CS-C. There was a significant stocking system-species mixture interaction in the final fasted LW achieved by heifers. Final fasted LW was significantly lower for CS-C than CA-C heifers (283 vs 323 (±9.7) kg), but did not differ between CS-R and CA-R (332 vs 330 (±9.7) kg, respectively). The digestibility of diet OM was similar for both continuously and rotationally stocked sheep (84.4 vs 83.2 %, respectively). Cattle diet OMO was 76.5, 74.7, 79.4 and 77.8 for CA-C, CS-C, CA-R and CS-R respectively (P>0.05). Differences in OMI followed a similar pattern to daily LWG. Mean daily OMI was 8.98, 6.24, 8.80 and 9.45 (±0.40) kg for CA-C, CS-C, CA-R and CS-R, respectively. Clover content of the diet of CA-C heifers was three times higher than that of CS-C heifers (30.7 vs 10.4 % OM; P<0.05); there was no difference in clover content of diets of CS-R and CA-R heifers (21.5 vs 23.9 % OM, respectively). In both stocking systems LWG per ha was higher on CA than CS treatments. These results suggested that the disadvantage of selective clover grazing by sheep outweighed the advantages of sheep grazing around cattle dung patches under continuous stocking. Under rotational stocking, rapid diurnal changes in sward conditions probably limited selective grazing by both sheep and cattle such that there was no disadvantage to CS cattle. The results do not provide a basis for recommending grazing cattle with sheep rather than cattle alone, but do provide some basis for recommending co-grazing of sheep and cattle using rotational rather than continuous stocking.

Die semiaride Steppe der Inneren Mongolei (China) ist ein gefährdetes Ökosystem. Der Wandel vom traditionellen nomadischen Lebensstil hin zur konventionellen Landwirtschaft überlastet die Steppe und führt zu Degradierung und Desertifikation. Besonders die intensive Beweidung belastet die weiten Grasflächen und mindert deren natürliches Potential Kohlen-stoff (C) im Boden zu speichern. Um den Einfluss unterschiedlicher Beweidungsintensitäten auf die semiaride Steppe zu untersuchen, wurden im Rahmen des Projektes Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate (MAGIM) das Einzugsgebiet des Xilin Flusses in der Inneren Mongolei von 2004 bis 2009 untersucht. Dafür wurden u. a. meteorologische und Eddykovarianz-Messungen an definierten Standorten durchgeführt. Ziel dieser Messungen war es, die Unterschiede im Energiehaushalt und den Kohlendioxid- und Wasserflüssen (CO2- und H2O-Flüsse) für die dominanten Steppenarten und unter verschiedenen Beweidungsintensitäten zu erfassen. Die Schließung der Energiebilanz ergab eine Schließungslücke von 10 – 30% in Abhängigkeit der meteorologischen Bedingungen, wobei die Lücke unter feuchten Bedingungen kleiner ist. Die gemessenen CO2- und H2O-Flüsse sind klein im Vergleich zu Grasländern in den gemäßigten Zonen und reagieren sensitiv auf Veränderungen der Einflussfaktoren. Dabei ist die Evapotranspiration (ET) eng an den eingehenden Niederschlag (P) gekoppelt und über längere Zeiträume wie ein Jahr entspricht ET dem P (ET: 185,7 mm a-1 bis 242 mm a-1; P: 138 mm a-1 bis 332 mm a-1). Die Jahressummen für den Nettoökosystemaustausch (NEE) reichen von -10,7 g C m-2 a-1 (2005) bis -67,5 g C m-2 a-1 (2007) für die unbeweidete Steppe und charakterisieren diese als eine leichte Nettosenke für atmosphärisches CO2. Grundsätzlich zeigt die unbeweidete Steppe eine höherer C-Sequestrierung (maximale C-Sequestrierung im Mittel -0,06 g C m-2 s-1) als die beweidete Steppe (maximale C-Sequestrierung im Mittel -0,02 g C m-2 s-1). Die Messergebnisse zeigen, dass die Steppe unter trockenen Verhältnissen zur CO2-Quelle wird, unter erhöhten Niederschlagsbedingungen zur CO2-Senke und die Beweidung die C-Sequestrierung des Ökosystems unter beiden Bedingungen einschränkt. Im Vergleich der beiden Steppenarten (Leymus chinensis und Stipa grandis) konnte für Leymus chinensis eine höhere Trockentoleranz beobachtet werden. Diese führt zu einer höheren C-Sequestrierung unter trockeneren Verhältnissen. Unabhängig von der Steppenart sind die wichtigsten Einflüsse auf das Ökosystem die Bodenfeuchte, die vom eingehenden P abhängt, die Temperatur (T) und die Beweidung. Diese Faktoren können dabei nicht unabhängig voneinander betrachtet werden. Der Einfluss durch die Beweidung beeinflusst das Ökosystem nachhaltig, wobei die Intensität und die Dauer (Jahre) der Beweidung entscheidend sind, da nicht nur die oberirdische Biomasse reduziert wird, sondern gleichzeitig die Bodeneigenschaften. Um die Sensitivität auf den CO2- und H2O-Austausch der semiariden Steppe über die Messungen hinaus abzuschätzen, wurden Simulationen mit den Modellen BROOK90 und DAILYDAYCENT (DDC) durchgeführt. Beide Modelle konnten gut an die Bedingungen der semiariden Steppe angepasst werden, wobei die Übereinstimmung zwischen der gemessenen und modellierten ET für BROOK90 besser war (r2 = 0,7) als für DDC (r2= 0,34). Beide Modelle konnten gut die Dynamik der ET-Messungen wiedergeben. Die Sensitivitätsanalyse hat gezeigt, dass die Beziehung zwischen P und ET entscheidend für das Ökosystem ist und sich Änderungen in der T nur zum Ende und Beginn der Vegetationsperiode auf den Wasseraustausch auswirken. DDC konnte sehr gut den gemessenen CO2-Austausch simulieren. Die Ergebnisse zeigen die Sensitivität gegenüber den klimatischen Faktoren T, P und der Beweidung. Die CO2-Flüsse werden durch hohe Beweidungsintensitäten so stark minimiert, dass andere Einflussfaktoren dahinter zurücktreten. Bei leichten Beweidungsintensitäten wirkt sich dagegen besonders der P auf die Austauschprozesse aus. Die DDC-Ergebnisse zeigen, dass unter den derzeitigen Bedingungen der bodenorganische Kohlenstoff (SOC) verringert wird, also C aus dem Boden freigesetzt wird. Auch unter unbeweideten Verhältnissen steigt der SOC nicht wieder auf das Ausgangsniveau (von vor der Beweidung) an. Die Ergebnisse zeigten, dass die C-Sequestrierung der Steppe nur erhöht werden kann, wenn der P steigt, die T in einem Optimumbereich (+/- 2°C) bleibt und die Beweidung minimiert wird. Die Messungen und Modellergebnisse zeigen, dass der Niederschlag der limitierende Faktor der semiariden Steppe ist. P bestimmt die Bodenfeuchte, diese wiederum beeinflusst das Pflanzenwachstum und somit den CO2- und H2O-Austausch der Pflanzen. Die Beweidung strapaziert das Ökosystem und reduziert dadurch die CO2- und H2O-Flüsse und verändert die Bodeneigenschaften nachhaltig. Unabhängig von der klimatischen Entwicklung, ist die derzeitige überwiegend hohe Beweidungsintensität der Steppe eine Belastung für das Ökosystem und schränkt das Pflanzenwachstum langfristig ein, was u. a. die Desertifikation begünstigt. / Semiarid grasslands in Inner Mongolia (China) are degrading. The change from the traditional Nomadic lifestyle to conventional agriculture stresses the semiarid grasslands and increases desertification. In particular, intense grazing of the semiarid grasslands reduces their potential of storing carbon (C) in the soil. In the project Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate (MAGIM) a team of scientists researched the catchment area of the Xilin River to investigate impacts of different grazing intensities on semiarid grasslands. Meteorological and eddy covariance measurements took place from 2004 to 2009. The aim of the measurements was to examine the energy balance and the exchange of the carbon dioxide (CO2) and water (H2O) fluxes of the dominant grasslands in Inner Mongolia under different grazing intensities. The energy balance could be closed by 70 – 90% depending on the driving factors. The energy balance shows a smaller gap for moist conditions. The CO2 und H2O fluxes in the study area are much smaller than in temperate grasslands and show a high sensitivity towards the driving factors. Evapotranspiration (ET) is closely connected to the precipitation (P) and over longer periods of a year or more, ET nearly matches P (ET: 185.7 mm a-1 to 242 mm a-1; P: 138 mm a-1 to 332 mm a-1). The annual net ecosystem exchange (NEE) of ungrazed grassland ranges from -10.7 g C m-2 a-1 (2005) to -67.5 g C m-2 a-1 (2007), which makes the grassland a small CO2-sink. Overall, ungrazed grassland shows higher C sequestration (averaged maximum -0.06 g C m-2 s-1) than grazed grassland (averaged maximum -0.02 g C m-2 s-1). The measurements show the semiarid grassland as a CO2-source under dry conditions and as a CO2-sink under moist conditions, while grazing decreases the C sequestration for both climatic conditions. A comparison of the two dominant steppe types (Leymus chinensis and Stipa grandis) showed a higher tolerance for Leymus chinensis under dry conditions, which resulted in higher C sequestration for this vegetation. Besides the steppe type, the main driving factors are P, temperature (T) and grazing. These factors can not only be considered in isolation, but cross correlation needs to get considered as well. Grazing affects the sustainability of the ecosystem, with an increasing impact due to grazing intensity and duration (years). The impact of grazing influences the vegetation directly and shows indirect impacts for the soil properties. Simulations with the models BROOK90 and DAILYDAYCENT (DDC) enable a sensitivity analysis of CO2 and H2O fluxes of the semiarid grassland. Both models performed well, but BROOK90 showed a better fit to observed ET (r2 = 0.7) than DDC (r2= 0.34). Both models simulated the dynamics of the measured ET well. The sensitivity analysis showed a close relationship between P und ET and a smaller impact on ET due to a change in T. DDC performs well in the simulation of CO2 exchange dynamics of the semiarid grassland. The results show for high grazing intensities a decreasing influence of the other driving factors. A change in P has an influence on CO2 and H2O fluxes under low grazing intensities. The results also show a decrease in soil organic carbon (SOC) as grazing intensity increases (under current climatic conditions). An increase in SOC could only be achieved under an increase in P, an optimum T and low grazing intensities. The measurements and results of the simulations indentify P as the main driving factor controlling the CO2 and H2O fluxes in the semiarid grassland. P influences the soil moisture and this influences plant growth, which governs the CO2 and H2O exchange of the vegetation. Grazing decreases the CO2 and H2O exchange and affects the soil properties in the long term. Besides climate change, the current high grazing intensities of the semiarid grassland have a negative impact on the ecosystem, decreasing plant growth and increasing desertification.

Made available in DSpace on 2016-12-08T16:24:21Z (GMT). No. of bitstreams: 1 PGCA15MA158.pdf: 1126957 bytes, checksum: 8b5a7eec4c6afa6d4766dbe53aa6096b (MD5) Previous issue date: 2015-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Recent studies have shown that, in rotational stocking, post- grazing target should not exceed 40% of severity of defoliation of pre-grazing height. Although there is some evidence that from that level of defoliation animals start to graze undesirable horizons, there is not such evidence how these processes occurs at plant level. Thus, the aim of this study was to evaluate the dynamics of defoliation during the grazing down of kikuyu grass pastures (Pennisetum clandestinum Hochst. Ex. Chiov.), testing the hypothesis that the transition between the grazing horizons occurs when animals defoliate around 40% of initial height. The experiment was conducted using a pre-grazing height of 25 cm combined with levels of defoliation of 40, 50, 60 and 70% of the initial height. The experimental design was a randomized complete block with four treatments and three replications. Pastures were grazed down in 24 hours and assessments related to the dynamics of defoliation were conducted in four times during this period of occupation by using marked tillers technique. Were evaluated aspects of the frequency and intensity of defoliation by leaf category, tiller, extended tiller and stem, and the total grazed area, grazed area only once, grazed area two to three times and total regrazed area. It was found that the frequency of defoliation of individual tiller increased linearly with the stocking density and the technique of extended tiller underestimate the magnitude of frequency of defoliation regardless of severity of defoliation. From 40% of severity of defoliation, the probability of defoliation of senescent leaves and stems increased from two to three times, respectively. Both leaf and extended tiller were grazed, on average, with a relatively constant intensity. The transition between grazing horizons begins before 40% of severity of defoliation and to this severity is inevitable that approximately 25% of the grazed area suffer a second or third defoliation. It was concluded that, from the 40% of severity of defoliation, the exploration of lower horizons exceed the limit of 25% of the previously grazed area / Estudos recentes têm mostrado que, em lotação intermitente, a meta pós-pastejo não deve exceder 40% de rebaixamento da altura inicial dos pastos. Apesar de existirem indícios de que a partir dessa severidade de desfolhação os animais passam a pastejar horizontes indesejáveis, não existem evidências em nível de planta de como esses processos ocorrem. É por esse motivo que o objetivo deste trabalho foi avaliar a dinâmica de desfolhação durante o rebaixamento de pastos de capim-quicuiu (Pennisetum clandestinum Hochst. Ex. Chiov.), testando a hipótese de que a transição entre os horizontes de pastejo ocorre quando os animais desfolham em torno de 40% da altura em pré-pastejo. O experimento foi realizado utilizando uma altura em pré-pastejo de 25 cm combinada com severidades de desfolhação de 40, 50, 60 e 70% em relação à altura inicial. O delineamento experimental adotado foi de blocos completos casualizados com quatro tratamentos e três repetições. Cada pasto foi ocupado pelos animais por um período 24 horas e as avaliações referentes à dinâmica de desfolhação foram realizadas em quatro momentos durante esse período de ocupação por meio da técnica de perfilhos marcados. Foram avaliados aspectos relativos à frequência e intensidade de desfolhação por categoria de folha, perfilho, perfilho estendido e colmo, além da área pastejada total, área pastejada apenas uma, duas e três vezes e área repastejada total. Verificou-se que a frequência de desfolhação do perfilho individual aumentou linearmente com a densidade de lotação e que a técnica do perfilho estendido subestima a magnitude da frequência de desfolhação independente da severidade de desfolhação. A partir de 40% de severidade de desfolhação a ingestão de folhas senescentes e de colmos aumentou de duas a três vezes, respectivamente. Tanto as folhas como o perfilho estendido foram pastejados, em média, com uma intensidade relativamente constante. A transição entre horizontes de pastejo se inicia antes de 40% de rebaixamento dos pastos e até esta severidade de desfolhação é inevitável que aproximadamente 25% da área pastejada sofra uma segunda ou terceira desfolhação. É possível concluir que, a partir da severidade de 40% de desfolhação, a exploração de horizontes inferiores ultrapassa o limite de 25% da área previamente pastejada

Die semiaride Steppe der Inneren Mongolei (China) ist ein gefährdetes Ökosystem. Der Wandel vom traditionellen nomadischen Lebensstil hin zur konventionellen Landwirtschaft überlastet die Steppe und führt zu Degradierung und Desertifikation. Besonders die intensive Beweidung belastet die weiten Grasflächen und mindert deren natürliches Potential Kohlen-stoff (C) im Boden zu speichern. Um den Einfluss unterschiedlicher Beweidungsintensitäten auf die semiaride Steppe zu untersuchen, wurden im Rahmen des Projektes Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate (MAGIM) das Einzugsgebiet des Xilin Flusses in der Inneren Mongolei von 2004 bis 2009 untersucht. Dafür wurden u. a. meteorologische und Eddykovarianz-Messungen an definierten Standorten durchgeführt. Ziel dieser Messungen war es, die Unterschiede im Energiehaushalt und den Kohlendioxid- und Wasserflüssen (CO2- und H2O-Flüsse) für die dominanten Steppenarten und unter verschiedenen Beweidungsintensitäten zu erfassen. Die Schließung der Energiebilanz ergab eine Schließungslücke von 10 – 30% in Abhängigkeit der meteorologischen Bedingungen, wobei die Lücke unter feuchten Bedingungen kleiner ist. Die gemessenen CO2- und H2O-Flüsse sind klein im Vergleich zu Grasländern in den gemäßigten Zonen und reagieren sensitiv auf Veränderungen der Einflussfaktoren. Dabei ist die Evapotranspiration (ET) eng an den eingehenden Niederschlag (P) gekoppelt und über längere Zeiträume wie ein Jahr entspricht ET dem P (ET: 185,7 mm a-1 bis 242 mm a-1; P: 138 mm a-1 bis 332 mm a-1). Die Jahressummen für den Nettoökosystemaustausch (NEE) reichen von -10,7 g C m-2 a-1 (2005) bis -67,5 g C m-2 a-1 (2007) für die unbeweidete Steppe und charakterisieren diese als eine leichte Nettosenke für atmosphärisches CO2. Grundsätzlich zeigt die unbeweidete Steppe eine höherer C-Sequestrierung (maximale C-Sequestrierung im Mittel -0,06 g C m-2 s-1) als die beweidete Steppe (maximale C-Sequestrierung im Mittel -0,02 g C m-2 s-1). Die Messergebnisse zeigen, dass die Steppe unter trockenen Verhältnissen zur CO2-Quelle wird, unter erhöhten Niederschlagsbedingungen zur CO2-Senke und die Beweidung die C-Sequestrierung des Ökosystems unter beiden Bedingungen einschränkt. Im Vergleich der beiden Steppenarten (Leymus chinensis und Stipa grandis) konnte für Leymus chinensis eine höhere Trockentoleranz beobachtet werden. Diese führt zu einer höheren C-Sequestrierung unter trockeneren Verhältnissen. Unabhängig von der Steppenart sind die wichtigsten Einflüsse auf das Ökosystem die Bodenfeuchte, die vom eingehenden P abhängt, die Temperatur (T) und die Beweidung. Diese Faktoren können dabei nicht unabhängig voneinander betrachtet werden. Der Einfluss durch die Beweidung beeinflusst das Ökosystem nachhaltig, wobei die Intensität und die Dauer (Jahre) der Beweidung entscheidend sind, da nicht nur die oberirdische Biomasse reduziert wird, sondern gleichzeitig die Bodeneigenschaften. Um die Sensitivität auf den CO2- und H2O-Austausch der semiariden Steppe über die Messungen hinaus abzuschätzen, wurden Simulationen mit den Modellen BROOK90 und DAILYDAYCENT (DDC) durchgeführt. Beide Modelle konnten gut an die Bedingungen der semiariden Steppe angepasst werden, wobei die Übereinstimmung zwischen der gemessenen und modellierten ET für BROOK90 besser war (r2 = 0,7) als für DDC (r2= 0,34). Beide Modelle konnten gut die Dynamik der ET-Messungen wiedergeben. Die Sensitivitätsanalyse hat gezeigt, dass die Beziehung zwischen P und ET entscheidend für das Ökosystem ist und sich Änderungen in der T nur zum Ende und Beginn der Vegetationsperiode auf den Wasseraustausch auswirken. DDC konnte sehr gut den gemessenen CO2-Austausch simulieren. Die Ergebnisse zeigen die Sensitivität gegenüber den klimatischen Faktoren T, P und der Beweidung. Die CO2-Flüsse werden durch hohe Beweidungsintensitäten so stark minimiert, dass andere Einflussfaktoren dahinter zurücktreten. Bei leichten Beweidungsintensitäten wirkt sich dagegen besonders der P auf die Austauschprozesse aus. Die DDC-Ergebnisse zeigen, dass unter den derzeitigen Bedingungen der bodenorganische Kohlenstoff (SOC) verringert wird, also C aus dem Boden freigesetzt wird. Auch unter unbeweideten Verhältnissen steigt der SOC nicht wieder auf das Ausgangsniveau (von vor der Beweidung) an. Die Ergebnisse zeigten, dass die C-Sequestrierung der Steppe nur erhöht werden kann, wenn der P steigt, die T in einem Optimumbereich (+/- 2°C) bleibt und die Beweidung minimiert wird. Die Messungen und Modellergebnisse zeigen, dass der Niederschlag der limitierende Faktor der semiariden Steppe ist. P bestimmt die Bodenfeuchte, diese wiederum beeinflusst das Pflanzenwachstum und somit den CO2- und H2O-Austausch der Pflanzen. Die Beweidung strapaziert das Ökosystem und reduziert dadurch die CO2- und H2O-Flüsse und verändert die Bodeneigenschaften nachhaltig. Unabhängig von der klimatischen Entwicklung, ist die derzeitige überwiegend hohe Beweidungsintensität der Steppe eine Belastung für das Ökosystem und schränkt das Pflanzenwachstum langfristig ein, was u. a. die Desertifikation begünstigt. / Semiarid grasslands in Inner Mongolia (China) are degrading. The change from the traditional Nomadic lifestyle to conventional agriculture stresses the semiarid grasslands and increases desertification. In particular, intense grazing of the semiarid grasslands reduces their potential of storing carbon (C) in the soil. In the project Matter fluxes in grasslands of Inner Mongolia as influenced by stocking rate (MAGIM) a team of scientists researched the catchment area of the Xilin River to investigate impacts of different grazing intensities on semiarid grasslands. Meteorological and eddy covariance measurements took place from 2004 to 2009. The aim of the measurements was to examine the energy balance and the exchange of the carbon dioxide (CO2) and water (H2O) fluxes of the dominant grasslands in Inner Mongolia under different grazing intensities. The energy balance could be closed by 70 – 90% depending on the driving factors. The energy balance shows a smaller gap for moist conditions. The CO2 und H2O fluxes in the study area are much smaller than in temperate grasslands and show a high sensitivity towards the driving factors. Evapotranspiration (ET) is closely connected to the precipitation (P) and over longer periods of a year or more, ET nearly matches P (ET: 185.7 mm a-1 to 242 mm a-1; P: 138 mm a-1 to 332 mm a-1). The annual net ecosystem exchange (NEE) of ungrazed grassland ranges from -10.7 g C m-2 a-1 (2005) to -67.5 g C m-2 a-1 (2007), which makes the grassland a small CO2-sink. Overall, ungrazed grassland shows higher C sequestration (averaged maximum -0.06 g C m-2 s-1) than grazed grassland (averaged maximum -0.02 g C m-2 s-1). The measurements show the semiarid grassland as a CO2-source under dry conditions and as a CO2-sink under moist conditions, while grazing decreases the C sequestration for both climatic conditions. A comparison of the two dominant steppe types (Leymus chinensis and Stipa grandis) showed a higher tolerance for Leymus chinensis under dry conditions, which resulted in higher C sequestration for this vegetation. Besides the steppe type, the main driving factors are P, temperature (T) and grazing. These factors can not only be considered in isolation, but cross correlation needs to get considered as well. Grazing affects the sustainability of the ecosystem, with an increasing impact due to grazing intensity and duration (years). The impact of grazing influences the vegetation directly and shows indirect impacts for the soil properties. Simulations with the models BROOK90 and DAILYDAYCENT (DDC) enable a sensitivity analysis of CO2 and H2O fluxes of the semiarid grassland. Both models performed well, but BROOK90 showed a better fit to observed ET (r2 = 0.7) than DDC (r2= 0.34). Both models simulated the dynamics of the measured ET well. The sensitivity analysis showed a close relationship between P und ET and a smaller impact on ET due to a change in T. DDC performs well in the simulation of CO2 exchange dynamics of the semiarid grassland. The results show for high grazing intensities a decreasing influence of the other driving factors. A change in P has an influence on CO2 and H2O fluxes under low grazing intensities. The results also show a decrease in soil organic carbon (SOC) as grazing intensity increases (under current climatic conditions). An increase in SOC could only be achieved under an increase in P, an optimum T and low grazing intensities. The measurements and results of the simulations indentify P as the main driving factor controlling the CO2 and H2O fluxes in the semiarid grassland. P influences the soil moisture and this influences plant growth, which governs the CO2 and H2O exchange of the vegetation. Grazing decreases the CO2 and H2O exchange and affects the soil properties in the long term. Besides climate change, the current high grazing intensities of the semiarid grassland have a negative impact on the ecosystem, decreasing plant growth and increasing desertification.

Kalkbarrskogar är en sällsynt och artrik skogstyp i Sverige. Stora arealer finns i Jämtland. Skogstypen kalkbarrskog är prioriterade för områdesskydd och det finns därför ett behov att undersöka den. Studien genomfördes i samarbete med Länsstyrelsen i Jämtland. 45 prioritetsobjekt undersöktes genom GIS-baserade analyser. Målet var att undersöka objektens brukningshistorik för att undersöka eventuell påverkan på naturvärdena. Syftet var att utreda behovet av formellt områdesskydd. Samtliga objekt har fram till nutid aldrig blivit kalavverkade. 80 % var historiskt brukade med skogsbete och virkesuttag, vilket kan ha hållit skogarna glesa fram till 1960-talet. Studien kan inte visa om brukningshistoriken påverkat dagens naturvärden. Naturvärdena kan funnits innan brukandet startat, samt att andra miljöparametrar kan haft större betydelse. Idag är en femtedel av objekten helt eller delvis avverkade och en fjärdedel avverkningsanmälda. Studien kan styrka behovet av formellt områdesskydd på kalkbarrskogar i Jämtland eftersom det är ett motiverat alternativ för att naturvärdena bibehålls.

There is little evidence that the productivity of New Zealand beef herds has improved over time. Data from the NZ Meat and Wool Board’s Economic Service (2006) suggest that the average national calving percentage has declined over the last two decades. During the same period cattle carcass weights have increased but so too has the average cow live-weight which has resulted in increased maintenance costs of the cow herds. It is unclear whether production efficiency in the industry has improved or declined over time. The aim of this research was to develop means of improving productivity in commercial beef herds through practical methods of performance recording. The objectives were firstly to establish current management practices in commercial herds and secondly to develop an objective system for cow selection and culling which would have practical application in commercial herds. Beef management survey Ninety two commercial beef producers with more than 100 breeding cows from the greater Canterbury region of New Zealand were surveyed. Pasture control was the main reason given for owning a beef herd. Size and conformation were the main selection criteria for choosing replacement heifers and bulls. Over 80% of herds retained their own heifers as replacements and >60% mated yearling heifers to first calve at two years of age. Fertility was poor in the surveyed herds. In-calf rates at pregnancy testing averaged 88% for maiden heifers, 92% for rising second calvers and 93% for mixed age (m.a.) cows. There was no significant difference between in-calf rates of maiden heifers mated to first calve at two or three years of age; nor was there any significant difference between the re-breeding success of the two groups. Heifers mated at least one week earlier than m.a. cows, achieved a re-breeding success 4.7% greater (P<.01) than those mated at the same time. Reasons for cows not weaning a calf included wet dry (9.3% of pregnant cows wintered), pregnancy tested not-in-calf (7.4%) and dam death (2.6%). Only 87.9% of pregnant females wintered weaned a calf (89.4% of m.a. cows and 84.9% of heifers). Reasons why cows exited the herds included diagnosed empty (37.2% of all exits), involuntary culls (25.4%), sold wet dry (16.2%), deaths (13.1%) and poor calf production (5.1%). Vaccination was infrequent with clostridial vaccines the most common in m.a. cows (15.2%) and in calves (40.7%); vaccination against Leptospirosis was much less common. Very few of the surveyed farms used any system of performance recording; as a result there was very little performance-based selection or culling practiced. Evaluation of alternative measures of cow productivity Data from four performance recording beef herds were used to compare alternative measures of cow productivity with the industry standard which is calf weaning weight adjusted for sex (SOC) and age of calf and age of dam (AOD), i.e. the “200 day weight.” None of the alternative measures evaluated required knowledge of calving date and all were relatively easily obtainable in extensively managed beef herds. The assessment of cows was based not on their estimated breeding values but instead on their most probable producing ability which, as the sum of all of the permanent, repeatable aspects of the calf-rearing ability of the cow, explains considerably more of the variance of weaning weight than does breeding value alone. SOC and AOD-adjusted marking weight, weaning weight and average daily gain (ADG) between marking and weaning were the traits mostly highly correlated with the 200d wt of calves (r = 0.68, 0.90 and 0.74. respectively). An Extensively- Grazed-Cow-Weaning-Index of these three indicator traits was found to be more highly correlated than any of the individual traits on their own (r = 0.94). Index weights for the three indicator traits were calculated within each herd and then those within-herd index weights were regressed on readily obtainable herd descriptive variables to obtain a regression equation that could predict index weights for any herd. When the model was applied to data from two additional herd years not included in the original model, the EGCW Index was highly correlated with the 200d weights (r>0.90). Performance-based culling of previously unselected commercial beef herds based on the EGCW Index will result in improved productivity due to the moderately high repeatability of calf weaning weight. Objective data from extensively grazed commercial herds will also make possible the use of commercial herd data in genetic evaluations of herd sires.

Irish agriculture is becoming increasingly regulated, with restrictions on fertiliser application rates and stocking rates to reduce nitrate (NO₀⁻) leaching losses. However these regulations have been, to date, based on minimal field research. The purpose of this study was to determine the actual leaching losses of nitrate from Irish dairy pasture at a range of stocking rates, and to investigate the effectiveness of the nitrification inhibitor DCD at reducing nitrate leaching losses where these are deemed excessive. In grazed pastures, a major source of leached nitrate is the urine patch, where a high rate of N is applied in one application. This trial recorded the losses from urine and non-urine areas of pasture separately. Nitrate leaching losses from three soils were recorded using lysimeters at Johnstown Castle, Co. Wexford, over two years. Total nitrate losses were higher from the freely drained Clonakilty and Elton soils than from the heavy Rathangan soil. Mean nitrate losses from urine patches ranged from 16 - 233 kg nitrate-N / ha⁻¹, and were reduced by up to 53% when DCD was applied. DCD also reduced peak and mean nitrate-N concentrations in many cases. In addition, DCD halved the nitrous oxide (N₂O) emission factor on the Rathangan soil, caused increases in pasture N content, and increased herbage yield in some treatments. The distribution of urine patches under dairy grazing was recorded using GPS at Kilworth, Co. Cork. Cows were also found to deposit 0.359 urine patches per grazing hour. A model was produced to predict field-scale nitrate leaching losses from dairy pasture at a range of stocking rates. At 2.94 cows per hectare, the highest stocking rate, annual field N loss was below 34 kg nitrate-N ha⁻¹, mean drainage N concentrations were below 5.65 mg nitrate-N L⁻¹ (the EU drinking water guideline value), and the worst-case-scenario autumn peak concentration did not exceed 21.55 mg nitrate-N L⁻¹ (above the EU Maximum Allowable Concentration (MAC) but below the World Health Organisation (WHO) drinking water limit). DCD reduced total annual field N loss by 21% (a conservative estimate), and also reduced mean and peak nitrate concentrations. Provided fertiliser application rates are at or below 291 kg N ha⁻¹, and based on current legislative values for drinking water quality, this trial does not support any blanket restrictions on the stocking rate of Irish dairy farms. However where particularly high water quality is required, DCD shows potential as a useful tool to achieve low nitrate concentrations.