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Differential effects of nutrient addition and woody plant encroachment on grassland soil, litter and plant dynamics across a precipitation gradient
Pedobiologia ( IF 2.3 ) Pub Date : 2021-03-27 , DOI: 10.1016/j.pedobi.2021.150726
Tiffany Pillay , David Ward , Admore Mureva , Michael Cramer

Interactions between woody plant encroachment and nutrient availability may vary along precipitation gradients. Furthermore, with predicted increases in N deposition due to increasing industrial emissions and changes in land use, potential increases in N storage and cycling are expected. We conducted a two-year field experiment that tested whether nitrogen (N) and phosphorus (P) addition and woody plant encroachment had independent effects on grasslands along a precipitation gradient. We added these nutrients to adjacent encroached and open grasslands (ranging from 300 to 1500 mm mean annual precipitation). We compared differential responses to fertilizer addition and encroachment in terms of soil N stocks and soil P, litter % N and C:N ratio (index of decomposition), plant productivity and species richness. In addition, we determined whether there were trends in responses to increased nutrient availability for encroached versus open grasslands across the above-mentioned precipitation gradient. Soil N stocks were on average 15 times higher in the high precipitation sites regardless of nutrient addition or encroachment status. Larger variation in soil P was noted at the high precipitation sites, with some evidence of P-limitation in the encroached area with the highest precipitation. Fertilization increased grass biomass and reduced species richness in the high precipitation sites only. Overall, increased nutrient availability was found to be of importance in high precipitation sites only, possibly due to water scarcity at the low precipitation sites. We found significant positive effects of encroachment on litter % N (quality), C:N ratios and forb cover across the precipitation gradient. The purportedly beneficial effects of encroachment on litter and plant species richness was more pronounced at the high-precipitation sites.



中文翻译:

降雨梯度下养分添加和木本植物入侵对草地土壤,凋落物和植物动态的不同影响

木本植物入侵与养分供应之间的相互作用可能会随着降水梯度的变化而变化。此外,由于工业排放量的增加和土地利用的变化,预计氮沉降量会增加,因此氮存储和循环的潜力有望增加。我们进行了为期两年的野外试验,测试了氮(N)和磷(P)的添加以及木本植物的侵染是否对沿降水梯度的草地具有独立的影响。我们将这些养分添加到邻近的被侵蚀和开阔的草原(年平均降水量在300至1500毫米之间)。我们比较了土壤氮素存量和土壤磷,凋落物%N和C:N之比(分解指数),植物生产力和物种丰富度对肥料添加和侵蚀的不同响应。此外,我们确定了在上述降水梯度下,侵蚀草地和开阔草地的养分利用率增加趋势是否存在。高养分地区的土壤氮素存量平均高出15倍,而与养分添加或侵蚀状态无关。在高降水量的地方,土壤P的变化较大,并且有证据表明在最高降水量的侵蚀区P受到限制。施肥仅在高降水量地点增加了草的生物量,并减少了物种丰富度。总的来说,增加养分的利用率仅在高降水量地区才很重要,这可能是由于低降水量地区缺水造成的。我们发现侵害对凋落物的%N(质量),C有明显的积极影响:N比值和前缘覆盖整个降水梯度。据称,侵蚀对凋落物和植物物种丰富度的有益影响在高降水量地点更为明显。

更新日期:2021-04-06
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