安氏薮羚的性二型对采食行为的影响(英文)

安氏薮羚(Tragelaphus angasii)是具有性别体二型的动物,其体型大小的差异可能对采食行为和生境选择有显著影响.利用连续行为取样法检测了雌雄个体在生境和植物利用上的差异,记录采食植物种类和采食高度并进行了性别间比较.在每个采食周期末,采用点中心方形样方法(PCQ)对植被进行一次调查,利用判别函数分析鉴别雌雄个体之间在种类和高度上是否存在差异.雌羚在三类生境中花费的采食时间相似,但雄羚表现出对砂地林的偏好.另外,在同一生境内雄羚利用更多的木本种类且采食较高的部位,而雌羚喜欢采食低层草本植物.安氏薮羚雌雄个体在生境内具有食性(采食种类)和空间(生境斑块)上的分离.我们认为这是由性二型引起的性别间营养与能量需求差异和不同繁殖策略造成的,最终使得精食者动物在具有复杂结构空间异质性的生境内表现为空间性别分离     

普氏原羚的采食对策

从1998年8月到2000年6月,我们在青海省共和县和海晏县利用系统取样法测定了植物的地上生物量,利用粪样显微组织学分析法、目标动物记录法研究了约200只普氏原羚的食物组成和采食时间,同时研究了普氏原羚对采食生境的选择。我们发现：（1）采食是普氏原羚的主要活动之一,占其活动时间的40.0%-65.6%。普氏原羚晨昏采食时间超过总采食时间82.9%;（2）普氏原羚在人为干扰小、食物丰富度高的地方采集,人为干扰与食物丰富度对普氏原羚的采食活动影响显著（P＜0.01）;（3）普氏原羚是广食性物种,共取食16科50种植物,其食物组成季节性差异极为显著（P＜0.01）;（4）食物资源影响普氏原羚的食物组成。普氏原羚的食物中从11月份到第二年5月会出现替代性食物狼毒和马蔺,食物中狼毒和马蔺的比例随食物资源的下降而上升;在5月份,偶吃性食物沙蒿所占比例最大,为13.8%;（5）普氏原羚选择芨藤草草原以及其它食物丰富度高、隐蔽条件好和人类干扰少的生境作为采食区;几乎不在围栏内采食,但常在距离围栏1km内的生境中采食,对距离围栏1km以上的采食生境的选择为随机选择;普氏原羚不在沙丘中采食,而在沙丘边缘的生态交错带采食。基于以上结果,我们认为：人类活动和食物资源量对普氏原羚的采食对策影响显著。     

蒙古野驴的秋季食性分析

2006 年9 月在新疆卡拉麦里山有蹄类野生动物保护区内采集了25 堆蒙古野驴粪便和10 科共29 种植物标本,采用粪便显微组织学分析方法分析了蒙古野驴的秋季食性,并初步探讨了其食性与周围环境的关系。结果表明,蒙古野驴秋季食性广, 共采食8 科26 种植物。这些植物按照其在食物组成中的比例可分为3 大类:主要食物为梭梭、针茅、驼绒藜, 共占食物组成的61.3% ;常采食植物为柽柳、角果藜、蒿、琵琶柴、芨芨草等11种,共占食物组成的33.3%; 少见采食的植物为盐爪爪、獐毛、顶羽菊、黑果枸杞、里海盐爪爪等12 种,共占食物组成的6.7% 。按科别而论,蒙古野驴采食最多的是藜科植物,其次是禾本科植物。从被采食植物的分布区域分析,其采食区域广阔,包括了保护区内所有的生境类型。      

秦岭羚牛的食性

在佛坪自然保护区对秦岭羚牛的食性研究中,记录到羚牛采食161种植物,其中草本占32．9％,木本占62．7％,苔藓植物和蕨类植物牛4．4％。羚牛的食物呈季节性变化,它采食的植物种类在春季、夏季比秋季多、冬季多。羚牛是广食性的植食动物,但它对所采食植物的部位具有一定的选择性,主要以采食植物的嫩枝叶为主,同时还有啃食树皮的习性。野外见到羚牛以直接饮水或舔雪的方式来补充对水份的需求。     

东北虎豹国家公园东部有蹄类栖息地的灌草层食物资源的量与质

东北虎和东北豹主要捕食马鹿、梅花鹿、狍  及野猪等大中型有蹄类动物,而这些有蹄类的生存依赖森林灌草层的植食性食物资源,形成了东北亚温带森林生态系统完整的啃食食物链 (grazing food chain) 主体。本研究通过对建设中的东北虎豹国家公园东部地区有蹄类栖息地的灌草层植物进行本底调查,获得有蹄类动物的食物资源基线数据。2015年及2016年生长季,在东北虎豹国家公园东部,随机选择141个样地嵌套496条样线,1948个样方,对不同森林结构 (郁闭林及开阔生境,开阔生境包括林窗、林缘和河岸带) 的灌草层植物生物量、食物类别组成 (嫩枝叶、禾莎草、杂类草和蕨类) 及碳、氮含量进行调查分析。研究结果显示：灌草层生物量在开阔生境显著高于郁闭林下 (94.91 g/m² vs. 30.15 g/m²),达到3.15倍。三种开阔生境下的灌草层食物资源类别组成差异显著,在林窗内以嫩枝叶优势,在林缘以杂类草占优势,在河岸带以蕨类占优势。灌草层中杂类草和嫩枝叶平均氮含量高,杂类草碳含量低、C/N低;四类植物热值均超17kJ/g,其中嫩枝叶最高。嫩枝叶、杂类草占优势的高生物量 (生物量大于40 g/m²) 斑块占郁闭林下的16 %、占开阔生境的50 %左右,可能是精食者 (browser) 的取食热点区域。建议在未来国家公园建设中,在合适的地段保留一定的开阔生境,为梅花鹿等食草动物补充高质量的灌草层食物资源斑块,促进有蹄类动物种群发展,并以此为基础恢复虎豹种群。     

南非克留格尔国家公园马羚的种群下降:一个备择假说

本研究报道了1979年以来南非克留格尔国家公园暂时性沼泽边界对马羚( Hippotragus equinus equinus)种群下降的影响。干旱和由此导致的生境退化以及随之产生的食草动物之间的采食竞争是解释马羚种群数量下降的可能假说。我们认为,确定马羚的生境斑块选择并测定影响暂时性沼泽边界变化与马羚种群下降的关联性因子,可解释马羚种群下降的备择假说。在北部平原区,边界呈斑块状分布的沼泽是马羚的高矿质采食源。实施狩猎管理工程期间,人工做成的大多数水道分布于沼泽边界及其附近,造成马羚与其它食草动物的采食竞争和天敌捕食压力的增高。旱季降雨的缺乏,加上沼泽边界区域采食竞争以及天敌捕食压力,是引发马羚在北部平原生境普遍退化之前其种群提前下降的因素[动物学报52 (2) : 406 -409 , 2006]。     

喀斯特石山生境中熊猴的雨季食物组成

开展食物组成研究为人们了解灵长类对栖息地的反应提供了很好的途径,对深刻理解动物的行为可塑性及适应性具有重要意义。猕猴属(Macaca)为果食性灵长类,但是不同种类的食性差异很大;即使便同一物种,其不同地理种群也因其栖息环境不同,食物组成存在差异。一般说来,热带地区的种类比生活在较高纬度的种类采食更多的果实。于2012年7—9月,采用瞬时扫描法对广西弄岗自然保护区石山中的两群熊猴(Macaca assamensis)进行了跟踪和观察,对猴群的雨季食物组成及其日时段变化规律进行了研究。结果表明:研究期间熊猴共采食45种植物,其中乔木30种,灌木3种,藤本11种,草本1种。平均每月采食植物22.3种。嫩叶和果实是熊猴的主要食物,分别占食物组成的52.4%和46.1%(其中未成熟果实占21.3%,成熟果实占24.8%)。另外,花占食物组成的0.9%,成熟叶和其它部位分别占0.3%。石山特有植物芸香竹(Bonia saxatilis)的嫩叶提供了43.8%的食物。9种主要植物分别占食物组成的2%,共为猴群提供了85.5%的食物。分析还发现熊猴并不是严格按照环境中的植物生物量来选择食物。嫩叶在弄岗熊猴的食物中的比例高于其他地理种群,而果实低于其他地理种群,这可能与喀斯特石山中果实的丰富度和可利用性较低有关。熊猴一天中不同时间段的食物组成并不相同,主要表现在:熊猴上午时间段对成熟果实和总果实的采食比例高于下午时间段,而嫩叶的采食比例低于下午时间段。另外,不同时间段的食物组成受外界温度的影响,表现为温度与嫩叶的觅食比例成正比,与成熟果实和总果实的觅食比例成反比。这可能与猴群采取的能量平衡策略有关。对熊猴的食物组成的日时段变化规律进行首次报道,研究结果将有助于深入理解熊猴对喀斯特石山生境的适应策略。     

蒙古野驴、鹅喉羚和家畜的食物重叠

采用粪样显微分析技术研究了新疆卡拉麦里山有蹄类自然保护区及周边区域蒙古野驴、鹅喉羚及家羊、家马和家骆驼3种家养有蹄类春季、秋季和冬季食性组成及食物生态位。结果发现：（1）蒙古野驴、鹅喉羚和家畜主要采食针茅、驼绒藜、蒿和梭梭,但是,它们采食的植物科数和种数都不相同,各植物种类在食谱中所占的比例不同;（2）各个季节有蹄类动物两两之间的食物生态位重叠均在0．8以上,最低为0．832（冬季鹅喉羚和家马）,最高达到0．986（秋季蒙古野驴和家羊;秋季家马和家羊）,五种有蹄类之间的食物生态位重叠度也达到了0．3以上。表明在卡拉麦里山有蹄类自然保护区,上述野生动物及季节性进入该自然保护区的家畜之间均存在食物竞争;冬季积雪深,食物短缺,荒漠有蹄类易因冻饿及疾病等造成死亡。因此,应采取限制秋冬季进入该自然保护区,家畜数量及调整放牧区域等保护管理措施,对该区域荒漠有蹄类动物实施有效保护[动物学报54（6）：941-954,2008]。     

新疆北部鹅喉羚的食性分析

2006年10月至2007年8月,作者采用粪便显微分析法研究了新疆卡拉麦里山有蹄类保护区鹅喉羚的四季食性以及冬季绵羊的食性.结果发现:鹅喉羚共采食16科47种植物;不同季节间鹅喉羚食性有明显变化,秋季采食7科24种植物,冬季采食6科17种植物,春季采食16科41种植物,夏季采食12科30种植物;藜科、禾本科植物是鹅喉羚全年的主要食物来源,占鹅喉羚总采食量的38.8～85.1%,非禾本科草本植物也在鹅喉羚食物组成中占有重要地位;春季短命和类短命植物对鹅喉羚有重要意义,占春季采食量的27%.针茅在四季都是鹅喉羚采食的主要植物;春季和夏季鹅喉羚采食较多的驼绒藜,秋季和冬季梭梭被较多采食.由于干旱胁迫,春季、夏季和秋季鹅喉羚喜食含水量较高的多根葱、骆驼蹄瓣、粗枝猪毛菜等非禾本科草本植物.冬季鹅喉羚与绵羊间的生态位宽度相近,食物重叠指数高达76.6%,绵羊与鹅喉羚之间食物竞争明显.     

不同发情阶段雄性鹅喉羚的时间分配特征

以往研究表明受发情交配行为制约,一些雄性反刍动物在发情期食物摄入量明显降低。已有两个相关假说解释该现象:能量摄入最大化假说和能量保存假说。作者于2009 ～ 2010 年在卡拉麦里山有蹄类自然保护区研究了雄性鹅喉羚不同发情阶段的时间分配。结果表明雄羚发情期采食时间比例明显下降(37. 9% ),低于发情前期(63. 6% )和发情后期(65. 8% );发情期卧息时间比例(6. 0% )与发情后期相近(5. 4% ),明显低于发情前期(23.2% );发情前期至发情后期采食卧息时间比(分别为2. 7、6. 3、12. 1)显著增加;发情期雄羚站立和移动时间比例明显升高,采食行为时间占非发情行为时间主要部分(86. 4% ),且采食行为与发情行为显著相关。相比之下,雌羚不同发情阶段采食行为时间分配比例相似。总之,除必需投入的发情行为外,发情期雄羚最大化其能量摄入;发情行为的投入是导致发情期雄羚食物摄入量下降的主导因子,雄性能量摄入最大化假说更好地解释了发情期鹅喉羚所采取的能量策略。     

Inter- and intrahabitat dietary variability of chacma baboons (Papio ursinus) in South African savannas based on fecal delta13C, delta15N, and %N

Baboons are dietary generalists, consuming a wide range of food items in varying proportions. It is thus difficult to quantify and explain the dietary behavior of these primates. We present stable carbon (delta(13)C) and nitrogen (delta(15)N) isotopic data, and percentage nitrogen (%N), of feces from chacma baboons (Papio ursinus) living in two savanna environments of South Africa: the mountainous Waterberg region and the low-lying Kruger National Park. Baboons living in the more homogeneous landscapes of the Waterberg consume a more isotopically heterogeneous diet than their counterparts living in Kruger Park. Grasses and other C(4)-based foods comprise between approximately 10-20% (on average) of the bulk diet of Kruger Park baboons. Carbon isotopic data from the Waterberg suggest diets of approximately 30-50% grass, which is higher than generally reported for baboons across the African savanna. Based on observations of succulent-feeding, we propose that baboons in the Waterberg consume a mix of C(4) grasses and CAM-photosynthesizing succulents in combined proportions varying between approximately 5-75% (average, approximately 35%). Fecal delta(15)N of baboons is lower than that of sympatric ungulates, which may be due to a combination of low levels of faunivory, foraging on subterranean plant parts, or the use of human foods in the case of Kruger Park populations. Fecal N levels in baboons are consistently higher than those of sympatric ungulate herbivores, indicating that baboons consume a greater proportion of protein-rich foods than do other savanna mammals. These data suggest that chacma baboons adapt their dietary behavior so as to maximize protein intake, regardless of their environment.     

Stable isotope evidence for impala Aepyceros melampus diets at Akagera National Park,Rwanda

Stable isotope analysis of tooth enamel was used to investigate the relative proportions of grass and browse in seasonal and overall diets of impala Aepyceros melampus at Akagera National Park, Rwanda. Bulk enamel samples suggest that on average, impala ate c. 86% C₄ grass year‐round, far more than in most previously studied impala populations across Africa. Intra‐tooth samples show that seasonal changes in the proportion of C₄ grass versus C₃ browse are minimal (c. 10%), the diet being dominated by C₄ grass year‐round in contrast to other impala populations that consume ≥50% browse during the dry season. Intra‐tooth oxygen isotope values track carbon isotope changes to a moderate degree, but are not patterned clearly enough to permit identification of wet versus dry seasons. As other studies have shown that impala select high‐protein diets, the foraging behaviour at Akagera is probably because of the availability of palatable grass for much of the year in the edaphic grasslands around the lacustrine environments of the eastern portions of Akagera National Park.     

Landscape-scale feeding patterns of African elephant inferred from carbon isotope analysis of feces

The African elephant (Loxodonta africana) is a large-bodied, generalist herbivore that eats both browse and grass. The proportions of browse and grass consumed are largely expected to reflect the relative availability of these resources. We investigated variations in browse (C(3) biomass) and grass (C(4)) intake of the African elephant across seasons and habitats by stable carbon isotope analysis of elephant feces collected from Kruger National Park, South Africa. The results reflect a shift in diet from higher C(4) grass intake during wet season months to more C(3) browse-dominated diets in the dry season. Seasonal trends were correlated with changes in rainfall and with nitrogen (%N) content of available grasses, supporting predictions that grass is favored when its availability and nutritional value increase. However, switches to dry season browsing were significantly smaller in woodland and grassland habitats where tree communities are dominated by mopane (Colophospermum mopane), suggesting that grasses were favored here even in the dry season. Regional differences in diet did not reflect differences in grass biomass, tree density, or canopy cover. There was a consistent relationship between %C(4) intake and tree species diversity, implying that extensive browsing is avoided in habitats characterized by low tree species diversity and strong dominance patterns, i.e., mopane-dominated habitats. Although mopane is known to be a preferred species, maintaining dietary diversity appears to be a constraint to elephants, which they can overcome by supplementing their diets with less abundant resources (dry season grass). Such variations in feeding behavior likely influence the degree of impact on plant communities and can therefore provide key information for managing elephants over large, spatially diverse, areas.     

Distributional niche of relatively rare sable antelope in a South African savanna: habitat versus biotic relationships

The geographic distribution of a species is governed by climatic conditions, topography, resources and habitat structure determining the fundamental niche, while the local distribution expressed via home range occupation may be compressed by biotic interactions with competitors and predators, restricting the realised niche. Biotic influences could be especially important for relatively rare species. We investigated how rainfall, geology, land type and abundance of other ungulate species serving as competitors or prey for predators contributed to the patchy distribution of sable antelope herds within Kruger National Park. Data were provided by annual aerial surveys of ungulate populations conducted between 1978 and 1988. Sable herds were more commonly present on granitic and sandstone substrates than on more fertile basalt. They occurred both in the moist south‐west and dry north of the park. They were most abundant in sour bushveld and mopane savanna woodland, and mostly absent from knob thorn‐marula parkland. The presence of sable was negatively associated with high concentrations of impala and wildebeest, less consistently related to the abundance of zebra, and positively associated with the occurrence of buffalo herds. Best supported models included the separate effects of the most abundant grazers along with land type. Interspecific relationships seemed more consistent with vulnerability to predation as the underlying mechanism restricting the distribution of sable herds than with competitive displacement. Sable favoured land types distinct from those where wildebeest, the most preferred prey of lions, and impala, numerically the most important resident prey species, were most abundant. Hence the risk of predation, associated with habitat conditions where abundant prey species are most concentrated, can exert an overriding influence on the distribution of rarer species in terms of their home range occupation.     

Changing vulnerability to predation related to season and sex in an African ungulate assemblage

The consequences of predation for prey population dynamics depend on the extent to which this mortality is predisposed by malnutrition or senescence, or additive in the sense that animals that would otherwise not have died at that time were killed. In places lacking effective predators, few adult ungulates die during the summer or wet season months when food is plentifully available. Hence the seasonal distribution of predator kills as well as the age and sex classes of the prey indicates the extent to which malnutrition contributes to mortality as well as other influences on vulnerability. Using records of animal deaths assembled over 35 years in South Africa's Kruger National Park, these patterns were investigated for 12 ungulate species forming the prey of lions, and for three other large predators with respect to one prey species. Buffalo, kudu and giraffe were more strongly represented in kills made during the late dry season, while wildebeest and zebra made relatively greater contributions during the wet season. Impala, waterbuck, warthog and rarer antelope species became more prominent in kills during transitional periods between seasons. Five prey species showed an elevation in representation of males in lion kills during the mating season, as well as impala for all predator species. Females were more prominently represented in kills during the time of late gestation and parturition for three prey species. Hence reproductive activities as well as changing vegetation cover and food resources affected vulnerability to predation. Shifts in susceptibility to predation over the seasonal cycle corresponded with rainfall‐related variation in the annual representation of these ungulate species in lion kills. The availability of vulnerable prey species, age and sex classes at different stages of the seasonal cycle helps maintain a high abundance of lions. These factors contribute to the strong additive impact that predation has had on the abundance of some of these ungulate populations.     

Multiple Scales of Control on the Structure and Spatial Distribution of Woody Vegetation in African Savanna Watersheds

Factors controlling savanna woody vegetation structure vary at multiple spatial and temporal scales, and as a consequence, unraveling their combined effects has proven to be a classic challenge in savanna ecology. We used airborne LiDAR (light detection and ranging) to map three-dimensional woody vegetation structure throughout four savanna watersheds, each contrasting in geologic substrate and climate, in Kruger National Park, South Africa. By comparison of the four watersheds, we found that geologic substrate had a stronger effect than climate in determining watershed-scale differences in vegetation structural properties, including cover, height and crown density. Generalized Linear Models were used to assess the spatial distribution of woody vegetation structural properties, including cover, height and crown density, in relation to mapped hydrologic, topographic and fire history traits. For each substrate and climate combination, models incorporating topography, hydrology and fire history explained up to 30% of the remaining variation in woody canopy structure, but inclusion of a spatial autocovariate term further improved model performance. Both crown density and the cover of shorter woody canopies were determined more by unknown factors likely to be changing on smaller spatial scales, such as soil texture, herbivore abundance or fire behavior, than by our mapped regional-scale changes in topography and hydrology. We also detected patterns in spatial covariance at distances up to 50–450 m, depending on watershed and structural metric. Our results suggest that large-scale environmental factors play a smaller role than is often attributed to them in determining woody vegetation structure in southern African savannas. This highlights the need for more spatially-explicit, wide-area analyses using high resolution remote sensing techniques.     

Multi‐scale patterns and bush encroachment in an arid savanna with a shallow soil layer

Abstract. Question: Bush encroachment (i.e. an increase in density of woody plants often unpalatable to domestic livestock) is a serious problem in many savannas and threatens the livelihood of many pastoralists. Can we derive a better understanding of the factors causing bush encroachment by investigating the scale dependency of patterns and processes in savannas? Location: An arid savanna in the Khomas Hochland, Namibia. Methods: Patterns of bush, grass, and soil nutrient distribution were surveyed on several scales along a rainfall gradient, with emphasis on intraspecific interactions within the dominant woody species, Acacia reficiens. Results: Savannas can be interpreted as patch‐dynamic systems where landscapes are composed of many patches (a few ha in size) in different states of transition between grassy and woody dominance. Conclusions: In arid savannas, this patchiness is driven both by rainfall that is highly variable in space and time and by inter‐tree competition. Within the paradigm of patch‐dynamic savannas, bush encroachment is part of a cyclical succession between open savanna and woody dominance. The conversion from a patch of open savanna to a bush‐encroached area is initiated by the spatial and temporal overlap of several (localized) rainfall events sufficient for Acacia germination and establishment. With time, growth and self‐thinning will transform the bush‐encroached area into a mature Acacia stand and eventually into open savanna again. Patchiness is sustained due to the local rarity (and patchiness) of rainfall sufficient for germination of woody plants as well as by plant‐soil interactions.     

Oscillations in large mammal populations: are they related to predation or rainfall?

Cyclic population dynamics is relatively common among populations of small mammals in high latitudes but is not yet established among African savanna ungulates. However, oscillations may be expected in large mammal populations subject to quasi‐periodic oscillations in regional rainfall. We evaluated evidence for environmentally entrained oscillations in a large‐mammal predator–prey system in Kruger National Park (KNP), South Africa, where rainfall exhibits quasi‐periodic oscillations. The evaluation is based on analysis of comparative changes in the abundance of twelve ungulate species throughout South Africa's KNP using population counts over the period 1965–1996. We present evidence suggesting that (i) twelve ungulate populations display cyclic variability with half‐periods ranging between 10 and 18 years, (ii) this variability was associated with lagged rainfall between 3 and 10 years back in the past for different ungulate species, and (iii) the ungulate species respond in contrasting ways to rainfall, with some reaching highest abundance during periods of low rainfall and others under conditions of high rainfall. These findings are not consistent with the response pattern we would expect if the population oscillations were driven directly by the rainfall influence on food availability. Instead they seem to be an outcome of predator–prey interactions, which are entrained by the effect of rainfall on habitat conditions affecting the relative susceptibility of the different ungulate species to predation.     

A patch-dynamics approach to savanna dynamics and woody plant encroachment – Insights from an arid savanna

The coexistence of woody and grassy plants in savannas has often been attributed to a rooting-niche separation (two-layer hypothesis). Water was assumed to be the limiting resource for both growth forms and grasses were assumed to extract water from the upper soil layer and trees and bushes from the lower layers. Woody plant encroachment (i.e. an increase in density of woody plants often unpalatable to domestic livestock) is a serious problem in many savannas and is believed to be the result of overgrazing in ‘two-layer systems’. Recent research has questioned the universality of both the two-layer hypothesis and the hypothesis that overgrazing is the cause of woody plant encroachment.

We present an alternative hypothesis explaining both tree–grass coexistence and woody plant encroachment in arid savannas. We propose that woody plant encroachment is part of a cyclical succession between open savanna and woody dominance and is driven by two factors: rainfall that is highly variable in space and time, and inter-tree competition. In this case, savanna landscapes are composed of many patches (a few hectares in size) in different states of transition between grassy and woody dominance, i.e. we hypothesize that arid savannas are patch-dynamic systems. We summarize patterns of tree distribution observed in an arid savanna in Namibia and show that these patterns are in agreement with the patch-dynamic savanna hypothesis. We discuss the applicability of this hypothesis to fire-dominated savannas, in which rainfall variability is low and fire drives spatial heterogeneity.

We conclude that field studies are more likely to contribute to a general understanding of tree–grass coexistence and woody plant encroachment if they consider both primary (rain and nutrients) and secondary (fire and grazing) determinants of patch properties across different savannas.     

The influence of fire frequency on the structure and botanical composition of savanna ecosystems

Savannas cover 60% of the land surface in Southern Africa, with fires and herbivory playing a key role in their ecology. The Limpopo National Park (LNP) is a 10,000 km² conservation area in southern Mozambique and key to protecting savannas in the region. Fire is an important factor in LNP's landscapes, but little is known about its role in the park's ecology. In this study, we explored the interaction between fire frequency (FF), landscape type, and vegetation. To assess the FF, we analyzed ten years of the Moderate resolution Imaging Spectroradiometer (MODIS) burned area product (2003–2013). A stratified random sampling approach was used to assess biodiversity across three dominant landscapes (Nwambia Sandveld‐NS, Lebombo North‐LN, and Shrubveld Mopane on Calcrete‐C) and two FF levels (low—twice or less; and high—3 times or more, during 10 years). Six ha were sampled in each stratum, except for the LN versus high FF in which low accessibility allowed only 3 ha sampling. FF was higher in NS and LN landscapes, where 25% and 34% of the area, respectively, burned more than three times in 10 years. The landscape type was the main determinant of grass composition and biomass. However, in the sandy NS biomass was higher under high FF. The three landscapes supported three different tree/shrub communities, but FF resulted in compositional variations in NS and LN. Fire frequency had no marked influence on woody structural parameters (height, density, and phytomass). We concluded that the savannas in LNP are mainly driven by landscape type (geology), but FF may impose specific modifications. We recommend a fire laissez‐faire management system for most of the park and a long‐term monitoring system of vegetation to address vegetation changes related to fire. Fire management should be coordinated with the neighboring Kruger National Park, given its long history of fire management. Synthesis: This study revealed that grass and tree/shrub density, biomass, and composition in LNP are determined by the landscape type, but FF determines some important modifications. We conclude that at the current levels FF is not dramatically affecting the savanna ecosystem in the LNP (Figure 1). However, an increase in FF may drive key ecosystem changes in grass biomass and tree/shrub species composition, height, phytomass, and density.